Currently, it is required that display devices such as televisions and image devices connected to computers are light and slim, and consume a small amount of power. Accordingly, there is a need to produce excellent LCDs in order to obtain flat displays satisfying the above-mentioned requirements.
In the LCD, an alignment film having a surface that is inclined at a pretilt angle is provided to align liquid crystals in a predetermined direction.
With respect to a process of producing the alignment film, a process of rubbing a polymer resin film such as a polyimide resin formed on a substrate using cloths and the like in a predetermined direction, and a process of inclinedly depositing silicon dioxide (SiO2) to produce an alignment film are known. However, in the case of when the alignment film is produced using the rubbing treatment, there are problems in that the yield of products is reduced and contrast deteriorates due to contamination caused by impurities which are generated due to contact during the rubbing and the occurrence of static electricity. Additionally, the process using the inclined deposition is problematic in that production cost is increased and it is difficult to produce the alignment film having the large size, thus obstructing the production of the LCD having the large size.
In order to avoid the above-mentioned problems, currently, a method of producing the alignment film using a transcription process is in the spotlight. In the method of producing the alignment film using the transcription process, a lithograph body, having a surface of which protrusions and recesses to be transcribed are formed, is heated and pressed on a resin film formed on a substrate so as to form the protrusions and the recesses on a surface of the resin film. Generally, the surface of the alignment film, which is produced using the transcription body, has a structure where a plurality of blocks are repetitively formed in parallel on the substrate. However, in the LCD using the alignment film on which only the protrusions and the recesses are formed by the transcription process, the interface regulating force of the liquid crystal is poor and it is impossible to maintain desirable a pretilt angle (generally, 1° or more) by applying the external force or heat. Thus, the so-called domains may be generated.
JP-A-11-181127 discloses a method of producing a polymer-type alignment film that has a main chain including acrylate and methacrylate and a side chain having a photosensitive group such as a cinnamic acid group, and an alignment film produced using the method. However, the polymer is disadvantageous in that, since mobility is poor, it is difficult to obtain desirable alignment properties even though the polymer is exposed to light for a long time. The reason for this is as follows. Since the photosensitive group in the polymer is restrained in the main chain of the polymer, the photosensitive group cannot be rapidly reacted with polarized light when the polarized light is radiated. Accordingly, since it takes a long time to produce a network polymer, process efficiency is reduced. Additionally, if the alignment is finished after the alignment is performed for an insufficient time, the alignment of liquid crystals of the LCD is poor, thus reducing a dichroic ratio and a contrast.